Method for high-frequency tuning an electrical device

ABSTRACT

The invention relates to a method for RF matching of an RF plug connector ( 1 ), having a printed circuit board ( 3 ), with the printed circuit board having contact points ( 21 - 28 ) for RF contacts and contact points ( 31 - 38 ) for insulation-displacement contacts, with one contact point ( 21 - 28 ) for the RF contacts in each case being connected to a respective contact point ( 31 - 38 ) for the insulation-displacement contacts, and with capacitive coupling which causes near-end crosstalk occurring between the RF contacts, with at least one first conductor track ( 46 ), which is connected at only one end to a contact point ( 26 ) of an electrical contact, being arranged on the printed circuit board ( 3 ) and, together with at least one second conductor track ( 44 ) which is arranged on and/or in the printed circuit board ( 3 ), forming a capacitor (C 46 ), with at least one frequency-dependent parameter of the arrangement being measured and being compared with a nominal parameter, and the conductor track ( 46 ) with which contact is made on one side being partially removed or cut through as a function of the difference.

This application is a Continuation of U.S. Ser. No. 12/053,154, filed 21Mar. 2008, which is a Continuation of U.S. Ser. No. 10/547,498, filed 10May 2006, which is the National Stage of Application PCT/EP2004/001952,filed 27 Feb. 2004, and which application(s) are incorporated herein byreference.

BACKGROUND

The invention relates to a method for RF matching of an electricalarrangement, and to a printed circuit board which is suitable for thispurpose.

EP 0 525 703 A1 discloses a plug connection for computer networks in thedomestic area, comprising a male connector part and a female connectorpart, with a device for crosstalk compensation being arranged in theplug connection, by means of which the crosstalk attenuation between thetransmission conductor loop and the reception conductor loop can beincreased. For this purpose, a printed circuit board is arranged in thefemale connector part or in the male connector part of the plugconnection between the connections for the plug-in cable and theconnections for the wiring, with the conductor routes for thetransmission and reception conductor loops being largely physicallyseparated on the printed circuit board. The devices for crosstalkcompensation are, for example, discrete components such as capacitors orcoils, which are adjustable. The known plug connection has thedisadvantage that the discrete components are relatively expensive andlarge.

DE 100 51 097 A1 discloses an electrical plug connector comprising aplug connector housing, a printed circuit board with two sets of contactelements, with the first set of contact elements being arranged on thefront face of the printed circuit board and projecting into an openingin the plug connector housing, and the second set of contact elementsbeing arranged on the rear face of the printed circuit board, and thecontact elements in the second set being in the form ofinsulation-displacement contacts, with the plug connector having a cablemanager which has an opening through it and is provided on the frontface with guides for conductors which are intended to make contact withthe insulation-displacement contacts, with the guides being formed inthe area of the insulation-displacement contacts with recessed holdersfor the insulation-displacement contacts, and in which case the cablemanager can be matched to the plug connector housing.

Owing to the increasing bandwidth for data transmission intelecommunications and information technology, the conductors, contactsand conductor tracks have to be designed such that they are highlydefined with respect to one another, in order to comply with therequired values for the crosstalk attenuation.

This necessitates extremely tight tolerances, which can be complied withonly with difficulty during automated manufacturing processes.

SUMMARY

The invention is thus based on the technical problem of providing amethod for matching an RF plug connector, in particular an RJ-45 femaleconnector, having at least one printed circuit board, with the printedcircuit board having contact points for RF contacts and contact pointsfor the insulation-displacement contacts, and with one contact point forthe RF contacts in each case being connected to a respective contactpoint for the insulation-displacement contacts, and a printed circuitboard which is suitable for this purpose and by means of which the RFcharacteristics can be adjusted within a narrow tolerance band.

The technical problem is solved by the subject matters with the featuresof patent claims 1 and 11. Further advantageous refinements of theinvention are described in the dependent claims.

For this purpose, at least one first conductor track, which is connectedon only one side to a contact point of an electrical contact, isarranged on the printed circuit board and, together with at least onesecond conductor track which is arranged on or in the printed circuitboard, forms a capacitor, with at least one frequency-dependentparameter of the arrangement being measured, the frequency-dependentparameter being compared with a nominal parameter, and the conductortrack with which contact is made on one side being partially removed orcut through as a function of the difference. This makes it possible toform a matchable capacitor using simple and cost-effective means, and bymeans of which the RF response of the arrangement can be matched. Theconductor tracks are in this case preferably connected to the contactpoints of the RF contacts, since this means that the matchingcapacitances are closer to the location of the source of the crosstalk.However, in principle, they may also be connected to the contact pointsof the insulation-displacement contacts, which are electricallyconnected to the contact points of the RF contacts. It should be notedthat, in principle, it is sufficient to cut through or to remove oneconductor track of a capacitor in order to change the capacitance.

The opposite electrode of the capacitor is preferably likewise formed bya conductor track that is connected to a contact point on one side.

In a further preferred embodiment, at least one further second conductortrack is arranged in an internal layer in the printed circuit board andis electrically connected to the conductor track on the printed circuitboard. This represents capacitances connected in parallel, so that thetotal capacitance is added, thus allowing the formation of asufficiently large capacitance on a relatively small area.

In a further preferred embodiment, at least two independent capacitorswhich are formed by conductor tracks are arranged on the printed circuitboard, in order to carry out symmetrical trimming with respect toground.

In a further preferred embodiment, the frequency-dependent parameter isdetermined and adjusted on the unpopulated printed circuit board. Thisis based on the knowledge that, particularly in the case of RF plugconnectors, the printed circuit board itself is responsible for themajority of the RF tolerances. These tolerances are generally geometrictolerances of the layout elements, such as conductor tracks, andtolerances of the dielectric constant of the material of the printedcircuit board. Automatic measurement on an unpopulated printed circuitboard is considerably easier than on a populated printed circuit board,or even on a printed circuit board that has been installed in a housing.The overall arrangement can thus be matched even at an early stage inthe process of producing the printed circuit board. The feed andmeasurement are in this case preferably provided centrally in solderedeyes of the contact points.

In a further preferred embodiment, only a portion of the estimatedconductor track shortening that is necessary is carried out in a firststep. The frequency-dependent parameter is then measured once again. Themeasured change is then used to determine the remaining conductor tracklength that is still to be removed or to be cut. This also takes accountof the tolerances relating to the conductor tracks in the matchingprocess. The conductor track shortening can in this case also besubdivided into more than two steps.

In a further preferred embodiment, the final cut during the cutting ofthe conductor track is carried out in a broader manner than the firstcut. This broader cut minimizes the capacitive influence of the cut partof the conductor track.

In a further preferred embodiment, the near crosstalk is determined asthe frequency-dependent parameter, thus making the matching processeasier, since the parameter to be optimized directly is determined, sothat there is no need for any further estimates of the influence of theparameter on the near crosstalk as would be the case, for example, withpure capacitance measurement.

The conductor track is preferably cut by means of a laser, preferably bymeans of a short-wave laser with a wavelength that is shorter than 600nm. The use of a laser for cutting the conductor track is extremelyfast, and can easily be automated. In principle, the conductor track canalso be cut or removed mechanically, for example by means of milling orelectrically by using an overcurrent to burn through it.

In a further preferred embodiment, the laser has an associated opticalpositioning system. This results in the conductor track being cut in amore defined manner, without any damage to closely adjacent conductortracks and without the conductor track to be cut not being cutcompletely.

During removal or cutting of the conductor track, it is possible forcopper particles to be deposited on the printed circuit board, and thesein turn reduce the resistance to overvoltages. The cutting or removal ofthe conductor track is thus preferably followed by a cleaning step toremove the copper particles and/or any other contamination.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in more detail in the following textwith reference to a preferred exemplary embodiment. In the figure:

FIG. 1 shows an exploded illustration of a plug connector fortransmitting RF data (prior art),

FIG. 2 shows a printed circuit board for use in a plug connector shownin FIG. 1,

FIG. 3 shows a schematic equivalent circuit for the printed circuitboard,

FIG. 4 shows a schematic frequency response for the near crosstalk and

FIG. 5 shows a family of curves for the attenuation D of the nearcrosstalk as a function of the length of the conductor track to beremoved.

DETAILED DESCRIPTION

FIG. 1 shows an exploded illustration of a plug connector 1. The plugconnector 1 has a plug connector housing 2, a printed circuit board 3, ahold-down device 4 and a cable manager 5. The plug connector housing 2in the illustrated example is in the form of a female connector housingwith various latching and insertion means. The plug connector housing 2has a shielding plate 6 on the side surfaces. The printed circuit board3 is fitted on its front face with a first set of contacts 7, and isfitted on its rear face with a second set of insulation-displacementcontacts 8. One contact 7 in the first set is connected to a respectivecontact 8 in the second set. The printed circuit board 3 is theninserted into the plug connector housing 2. In the process, cylindricalpins 9 of the plug connector housing 2 pass through holes in the printedcircuit board 3, so that the plug connector housing 2 and the printedcircuit board 3 are adjusted and fixed with respect to one another. Thecontacts 7 (which are in the form of RF contacts) in the first set thenproject into an opening which is accessible from the front face of theplug connector housing. The hold-down device 4 is then pushed over thecontacts 8 in the second set, and is latched to the plug connectorhousing 2. For this purpose, the hold-down device 4 has latching tabs 10on the end face, and has openings 11 through it for theinsulation-displacement contacts 8. Furthermore, the hold-down device 4has two latching hooks 12, which are used for latching to the cablemanager 5.

FIG. 2 shows the unpopulated printed circuit board 3. The printedcircuit board 3 has eight contact points 21-28 and contact holes for theRF contacts, and eight contact points 31-38 for theinsulation-displacement contacts. The printed circuit board 3 also hasfurther plated-through holes 40 for connection of conductor tracks onthe front face and rear face and internal layers in the printed circuitboard, with the plated-through holes 40 being illustrated as smallcircles. The holes 41 in the printed circuit board 3 are in this caseillustrated as small squares. The conductor tracks which connect thecontact points 21-28 to their respectively associated contact point31-38 are not shown, with the exception of two parts of the contactpoints 24 and 35 since they are arranged on the rear face and/in theinternal layers of the printed circuit board. In addition to theelectrically connected conductor tracks between two contact points 21-28and 31-38, respectively, there are also four conductor tracks 43-46which are respectively connected on one side to a contact point 23-26.In this case, the two conductor tracks 44 and 46 form a capacitorbetween the contact points 24 and 26. In a corresponding way, the twoconductor tracks 43 and 45 form a capacitor between the contact points23 and 25. A further conductor track is preferably arranged in aninternal layer, is electrically connected to conductor track 44, and islocated under the conductor track 46. For circuitry purposes, thecontact points 21, 22; 23, 26; 24, 25 and 27, 28 and their respectivelyassociated contacts form a contact pair. In this case, the two outercontact pairs 21, 22 and 27, 28 are relatively uncritical with regard tonear crosstalk. The two inner and interleaved contact pairs 23, 26 and24, 25, on the other hand, are problematic. The capacitances which causedisturbances in this case are located between 23 and 24 as well asbetween 25 and 26, since the other couplings are negligible, owing tothe greater distances between them.

FIG. 3 shows the resultant equivalent circuit, including the schematictest layout. In this case, the capacitors C₄₆ and C₃₅ essentiallyrepresent capacitors formed by the conductor tracks 44 and 46 as well as43 and 45, respectively, while, in contrast, the capacitors C₃₄ and C₅₅,respectively, are formed by the adjacent contact points 23, 33 as wellas the associated conductor track, 24, 34 with the conductor track aswell as 25, 35 with the conductor track, and 26, 36 with the conductortrack. This bridge circuit can now be trimmed in order to force the nearcrosstalk below the required values. Before the trimming process, theasymmetry is first of all determined by determining the near crosstalkof one contact pair as a frequency-dependent parameter. In the presentcase, crosstalk is determined between the contact pair 23, 33 and 26, 36and the contact pair 24, 34; 25, 35. Since the measurement is preferablycarried out on the unpopulated printed circuit board 3, the contactpoints 33-36 are terminated with the correct impedance. The nearcrosstalk to the contact points 25, 24 is then measured, with RF signalsbeing injected into the contact points 23, 26, by means of a networkanalyzer which is symbolized in FIG. 3 by the frequency generator 50 andthe measurement device 51. The feeding and measurement of the RF signalsare in this case provided by means of a central contact in the soldereyes of the contact points 23-26.

FIG. 4 schematically shows the frequency response of the near crosstalkNEXT, with the profile a representing nominal near crosstalk, and theprofile b representing the measured actual near crosstalk for a measuredprinted circuit board. The nominal near crosstalk is determined, forexample, by means of a golden device. In this case, the measured nearcrosstalk is too high by an amount) NEXT, so that this must becompensated for by shortening the conductor tracks, thus reducing thecapacitance. The measure of how many millimeters of conductor trackcorrespond to what capacitance and thus to the near crosstalkattenuation D depends on the tolerances of the printed circuit board,such as the dielectric constant or the distance between the conductortracks. There is therefore no single straight line, but an entire familyof curves, as is illustrated schematically in FIG. 5. Since thetolerances are unknown, it may first of all be necessary to determinewhich curve is applicable to the printed circuit board to be matched.For this purpose, a piece of conductor track is first of all removed orcut through, and the measurements are then carried out once again. Theincrease in the attenuation D that is found can then be used todetermine the associated curve. If, on the other hand, the desiredattenuation is greater than that which can be achieved with the steepestcurve, the entire conductor track can be removed or cut through withoutany intermediate step. The method is then repeated on the othercapacitor.

The conductor track is preferably cut through by means of a short-wavelaser, whose power and focusing are matched to the copper track to becut such that, as far as possible, this is all that is removed. Theadvantage of a laser is its high speed with good reproducibility, sothat the matching process can easily be automated.

LIST OF REFERENCE SYMBOLS

-   1) Plug connector-   2) Plug connector housing-   3) Printed circuit board-   4) Hold-down device-   5) Cable manager-   6) Shielding plate-   7) Contacts-   8) Contacts-   9) Cylindrical pins-   10) Latching tabs-   11) Openings-   12) Latching hook-   21) Contact points (for RF contacts)-   22) Contact points (for RF contacts)-   23) Contact points (for RF contacts)-   24) Contact points (for RF contacts)-   25) Contact points (for RF contacts)-   26) Contact points (for RF contacts)-   27) Contact points (for RF contacts)-   28) Contact points (for RF contacts)-   31) Contact point (for an insulation-displacement contact)-   32) Contact point (for an insulation-displacement contact)-   33) Contact point (for an insulation-displacement contact)-   34) Contact point (for an insulation-displacement contact)-   35) Contact point (for an insulation-displacement contact)-   36) Contact point (for an insulation-displacement contact)-   37) Contact point (for an insulation-displacement contact)-   38) Contact point (for an insulation-displacement contact)-   40) Plated-through hole-   41) Hole-   43) Conductor track-   44) Conductor track-   45) Conductor track-   46) Conductor track-   50) Frequency generator-   51) Measurement device

1-15. (canceled)
 16. A method of compensating for crosstalk generated in an electrical plug, the method comprising: providing a printed circuit board including a plurality of conductive tracks, each track electrically connected between one of a plurality of plug contacts and a corresponding one of a plurality of insulation displacement contacts, the printed circuit board further including a capacitive compensation coupled across tracks associated with first and second wire pairs; measuring a nominal crosstalk effect of the first wire pair on the second wire pair; and upon determining that the nominal crosstalk effect exceeds a threshold, disconnecting at least a portion of the capacitive compensation from the associated tracks, thereby decreasing the nominal crosstalk effect to within a predetermined tolerance.
 17. The method of claim 16, wherein the electrical plug comprises a telecommunications jack.
 18. The method of claim 16, wherein determining a crosstalk effect comprises determining a near end crosstalk effect of the first wire pair on the second wire pair.
 19. The method of claim 16, wherein the capacitive compensation comprises closely-spaced conductor tracks positioned on an outer surface of the printed circuit board.
 20. The method of claim 19, wherein disconnecting at least a portion of the capacitive compensation includes removing the at least a portion of the capacitive compensation from the printed circuit board.
 21. The method of claim 20, wherein removing the at least a portion of the capacitive compensation from the printed circuit board comprises laser-trimming at least a portion of the closely-spaced conductor tracks.
 22. The method of claim 20, wherein removing the at least a portion of the capacitive compensation occurs after the printed circuit board is manufactured.
 23. The method of claim 16, wherein the printed circuit board comprises first, second, third, fourth, fifth, sixth, seventh, and eighth conductive tracks, and wherein the capacitive compensation is positioned between the third and fifth conductive tracks.
 24. The method of claim 16, further comprising, after measuring the nominal crosstalk effect of the first wire pair on the second wire pair, disconnecting a subportion of the capacitive compensation from the associated tracks; and measuring a second nominal crosstalk effect of the first wire pair on the second wire pair after disconnecting the subportion.
 25. The method of claim 24, wherein the portion of the capacitive compensation disconnected from the associated tracks is determined based on a function of the difference between the nominal crosstalk effect and the second nominal crosstalk effect.
 26. A circuit board useable within an electrical plug connector, the circuit board comprising: first, second, third, fourth, fifth sixth, seventh, and eighth plug contacts mounted at first contact locations; first, second, third, fourth, fifth sixth, seventh, and eighth insulation displacement contacts mounted at second contact points; first, second, third, fourth, fifth sixth, seventh, and eighth conductive tracks disposed on one or more layers of the circuit board and extending between corresponding first and second contact points; a capacitive coupling formed between two of the conductive tracks, the capacitive coupling including closely spaced conductor tracks each having a manufactured length, and wherein at least a portion of one of the closely spaced conductor tracks is removed after manufacturing to adjust a crosstalk compensation effect provided by the capacitive coupling.
 27. The circuit board of claim 26, wherein at least one of the closely spaced conductor tracks of the capacitive coupling is at least partially positioned on an outer layer of the circuit board.
 28. The circuit board of claim 26, wherein the capacitive coupling is positioned between the third and fifth conductive tracks.
 28. The circuit board of claim 28, further comprising a second capacitive coupling positioned between the fourth and sixth conductive tracks.
 28. The circuit board of claim 26, wherein the capacitive coupling is laser-trimmed after manufacturing to adjust the crosstalk compensation effect provided by the capacitive coupling.
 29. The circuit board of claim 26, wherein the crosstalk compensation effect provided by the capacitive coupling reduces a near end crosstalk generated by an electrical plug connector within which the circuit board is used.
 30. The circuit board of claim 26, wherein the plug contacts are mounted on a first side of the circuit board, and the insulation displacement connectors are mounted on a second side of the circuit board opposite the first side.
 31. The circuit board of claim 26, wherein the capacitive coupling includes a closely spaced conductor track positioned on an internal layer of the circuit board.
 32. An electrical plug connector comprising: a plug connector housing; a circuit board positioned within the plug connector housing, the circuit board including: first, second, third, fourth, fifth sixth, seventh, and eighth plug contacts mounted at first contact locations; first, second, third, fourth, fifth sixth, seventh, and eighth insulation displacement contacts mounted at second contact points; first, second, third, fourth, fifth sixth, seventh, and eighth conductive tracks disposed on one or more layers of the circuit board and extending between corresponding first and second contact points; a capacitive coupling formed between two of the conductive tracks, the capacitive coupling including closely spaced conductor tracks each having a manufactured length, and wherein at least a portion of one of the closely spaced conductor tracks is removed after manufacturing to adjust a crosstalk compensation effect provided by the capacitive coupling.
 33. The electrical plug connector of claim 32, further comprising a plurality of wires electrically connected to the insulation displacement contacts.
 34. The electrical plug connector of claim 33, further comprising a cable manager mountable to the housing, the cable manager having an opening through which the wires extend.
 35. The electrical plug connector of claim 32, wherein the capacitive coupling is laser-trimmed after manufacturing and prior to positioning the circuit board within the plug connector housing to adjust the crosstalk compensation effect provided by the capacitive coupling. 